U.S. patent application number 11/569139 was filed with the patent office on 2008-05-15 for susceptor for vapor-phase growth reactor.
This patent application is currently assigned to SUMCO CORPORATION. Invention is credited to Takayuki Dohi, Takashi Fujikawa, Masayuki Ishibashi, Seiji Sugimoto.
Application Number | 20080110401 11/569139 |
Document ID | / |
Family ID | 35394177 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080110401 |
Kind Code |
A1 |
Fujikawa; Takashi ; et
al. |
May 15, 2008 |
Susceptor For Vapor-Phase Growth Reactor
Abstract
In a susceptor (10) having a wafer pocket (101) for receiving a
wafer W at the time of vapor-phase growth, the wafer pocket has at
least a first pocket portion (102) for loading an outer
circumferential portion of the wafer and a second pocket portion
(103) formed to be lower than the first pocket and having a smaller
diameter than that of the first pocket portion, and a fluid passage
(105) having one end (105a) opening on a vertical wall (103a) of
said second pocket portion and the other end (105b) opening on a
back surface (104) or a side surface (106) of the susceptor is
formed.
Inventors: |
Fujikawa; Takashi; (Tokyo,
JP) ; Ishibashi; Masayuki; (Tokyo, JP) ; Dohi;
Takayuki; (Tokyo, JP) ; Sugimoto; Seiji;
(Tokyo, JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
SUMCO CORPORATION
Tokyo
JP
|
Family ID: |
35394177 |
Appl. No.: |
11/569139 |
Filed: |
May 17, 2005 |
PCT Filed: |
May 17, 2005 |
PCT NO: |
PCT/JP05/08979 |
371 Date: |
August 17, 2007 |
Current U.S.
Class: |
118/724 |
Current CPC
Class: |
H01L 21/68735 20130101;
C23C 16/4583 20130101; C30B 25/12 20130101; H01L 21/68785
20130101 |
Class at
Publication: |
118/724 |
International
Class: |
C23C 16/02 20060101
C23C016/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2004 |
JP |
2004-147638 |
Claims
1. A susceptor for vapor-phase growth having a wafer pocket for a
semiconductor wafer, comprising a fluid passage having a shape by
which radiant heat from a heat source does not directly irradiate a
back surface of said semiconductor wafer at the time of vapor-phase
growth is formed between a front surface and a back surface or a
side surface of said wafer pocket.
2. A susceptor for vapor-phase growth having a wafer pocket for a
semiconductor wafer, comprising said wafer pocket has at least a
first pocket portion for loading an outer circumferential portion
of said semiconductor wafer and a second pocket portion having a
smaller diameter than that of the first pocket portion and formed
to be lower than the first pocket portion; and a fluid passage
having one end opening on a vertical wall surface of said second
pocket portion and the other end opening on a back surface or a
side surface of the susceptor is formed.
3. The susceptor for vapor-phase growth as set forth in claim 2,
wherein an opening on the back surface side of said susceptor in
said fluid passage is formed on an outer side than a vertical wall
surface of said second pocket portion.
4. The susceptor for vapor-phase growth as set forth in claim 2,
wherein an opening on the back surface side of said susceptor in
said fluid passage is formed on an inner side than a vertical wall
surface of said second pocket portion.
5. The susceptor for vapor-phase growth as set forth claim 2,
wherein said fluid passage is formed to be a linear shape or a
nonlinear shape.
6. The susceptor for vapor-phase growth as set forth in claim 2,
wherein a plurality of said fluid passages are formed and one ends
of the fluid passages open substantially evenly along a
circumferential direction of the vertical wall surface of said
second pocket portion.
7. The susceptor for vapor-phase growth as set forth in claim 2,
wherein a plurality of said fluid passages are formed and one ends
of the fluid passages open in line in a vertical direction of the
vertical wall surface of said second pocket portion.
8. A susceptor for a vapor-phase growth having a wafer pocket for a
semiconductor wafer, comprising: at least a first structure having
a first pocket portion for loading an outer circumferential portion
of said semiconductor wafer and a second structure provided below
the first structure via a fluid passage configured by a clearance
between itself and the first structure; wherein one end of said
fluid passage opens on a vertical wall surface on a lower side of
said first pocket portion and the other end opens on a back surface
or a side surface of the susceptor.
9. The susceptor for vapor-phase growth as set forth in claim 8,
wherein said first structure and/or second structure in said fluid
passage have a support means formed for supporting said first
structure by said second structure.
10. The susceptor for vapor-phase growth as set forth in claim 8,
comprising an aligning means for determining a proper positional
relationship of said first structure and second structure.
11. The susceptor for vapor-phase growth as set forth in claim 9,
comprising an aligning means for determining a proper positional
relationship of said first structure and second structure.
Description
TECHNICAL FIELD
[0001] The present invention relates to a susceptor used for a
vapor-phase growth reactor for growing an epitaxial layer on a
surface of a silicon wafer (hereinafter, simply referred to as a
wafer) used for a semiconductor device and, particularly, relates
to a susceptor for a vapor-phase growth reactor capable of
suppressing rising of a dopant concentration of an outer
circumferential portion of an epitaxial film caused by
auto-doping.
BACKGROUND ART
[0002] As a vapor-phase growth reactor for growing an epitaxial
film having a high quality film property on a wafer surface, a
single wafer vapor-phase growth reactor is often used.
[0003] This single wafer vapor-phase growth reactor grows an
epitaxial film on a wafer surface by placing a wafer on a
disk-shaped susceptor formed by coating silicon carbide SiC on
graphite as a mother material in a channel-shaped chamber made by
quartz and bringing the wafer react with various material gases
passing through the chamber while heating the wafer by a heater
arranged on an outer surface of the chamber.
[0004] On a surface of the susceptor for receiving the wafer, a
recessed portion (depression) called a wafer pocket is formed,
which is a little larger than the wafer and has a depth of 1 mm or
so. By putting the wafer on the wafer pocket and holding the
susceptor in a material gas flow at a predetermined temperature,
growth of a silicon epitaxial layer is brought on the wafer
surface.
[0005] As the material gas of vapor-phase growth reaction, a
monosilane gas or a hydrogen-diluted chlorosilane based gas added
with a dopant material gas of diborane (P type), phosphine or
arsine (N type) is used. On the wafer surface, in addition to
silicon epitaxy formed by thermal CVD reaction, H.sub.2 is
generated in the case of a monosilane gas and HCl is generated in
the case of a chlorosilane based gas as a by-product. Therefore,
while silicon epitaxy proceeds on the wafer front surface, a Si--H
based atmosphere or a Si--H--Cl based atmosphere is formed on the
back surface of the wafer mainly due to flowing of the gas by
diffusion and deposition/etching reaction arises in a micro
aspect.
[0006] For example, when performing epitaxial growth of a lower
concentration than a dopant concentration of the wafer, such as a
case of performing epitaxial growth of a P type (having resistivity
of 1 .OMEGA.cm) film on a wafer of a dopant concentration of p type
(having resistivity of 5 m .OMEGA.cm), a phenomenon is observed
that the dopant concentration rises at a wafer outer
circumferential portion in the epitaxial layer.
[0007] This kind of phenomena are called auto-doping and the cause
is considered that a dopant seeds in the wafer are discharged in a
Si--H based atmosphere or a Si--H--Cl based atmosphere on the back
surface of the wafer and the dopant seeds flow to the wafer front
surface due to gas dispersion toward the front surface so as to
partially raise a dopant concentration in the vapor phase. As a
result, there arises a region where a dopant concentration becomes
uncontrollable in the epitaxial layer, which leads to a decline of
a non-defective rate.
[0008] To prevent variation of dopant densities of an epitaxial
layer by auto-doping as above, the present inventors have
previously proposed a susceptor having through hole portions formed
at an outermost circumferential portion of the wafer pocket (refer
to the patent article 1).
[0009] However, when forming through holes on a wafer pocket of a
susceptor, radiant heat from a heater, such as a halogen lamp,
provided below the susceptor passes through the through hole
portions to irradiate a back surface of a wafer and there arises a
temperature difference between a part facing to the through hole
portions of the wafer and other part. Consequently, there has been
a problem that unevenness of growth arises on the epitaxial layer
and a back surface of the wafer.
Patent Article 1: The Japanese Unexamined Patent Publication No.
10-223545
DISCLOSURE OF THE INVENTION
[0010] An object of the present invention is to provide a susceptor
for a vapor-phase growth reactor capable of preventing growth
unevenness of an epitaxial layer and a back surface of a wafer
while preventing unevenness of a dopant concentration in
auto-doping.
[0011] (1) To attain the above object, according to the present
invention, there is provided a susceptor for a vapor-phase growth
reactor, wherein a wafer pocket for accepting a semiconductor wafer
at the time of vapor-phase growth is formed, wherein a fluid
passage having a shape by which radiant heat from a beat source
does not directly irradiate a back surface of the semiconductor
wafer at the time of vapor-phase growth is formed between a front
surface and a back surface or a side surface of the wafer
pocket.
[0012] In the present invention, since a fluid passage is formed
between the front surface and back surface or side surface of the
wafer pocket, dopant seeds released from the wafer back surface are
discharged from the fluid passage without flowing to the front
surface of the wafer. As a result, a dopant concentration and
resistivity of the epitaxial layer can be unified without forming
an oxidized film for preventing auto-doping.
[0013] Also, the fluid passage according to the present invention
has a shape, by which radiant heat from a heat source does not
directly irradiate the wafer back surface at the time of
vapor-phase growth, so that temperature unevenness on the wafer
surface is suppressed and growth unevenness on the epitaxial layer
and wafer back surface can be prevented.
[0014] (2) As a shape of the fluid passage according to the present
invention, that is a shape, by which radiant heat from a heat
source does not directly irradiate the wafer back surface at the
time of vapor-phase growth, for example, when the wafer pocket is
configured to include at least a first pocket portion for loading
an outer circumferential portion of the wafer and a second pocket
portion having a smaller diameter than that of the first pocket
portion and formed to be lower than the first pocket portion, the
fluid passage can be configured to have one end opening on a
vertical wall of the second pocket portion and the other end
opening on the back surface or side surface of the susceptor.
[0015] When configuring the wafer pocket by a multi-shelf pocket
structure, a vertical wall is naturally formed on the pocket
portion and the vertical wall becomes substantially perpendicular
to the wafer back surface, so that irradiation of radiant heat from
the heat source directly to the wafer back surface is prevented.
Note that the other end of the fluid passage may open on the back
surface of the susceptor or on the side surface of the
susceptor.
[0016] Note that the first pocket portion according to the present
invention comprises a shelf portion for loading an outer
circumferential portion of the wafer and a vertical wall continuing
from the shelf portion to the outside. Also, the second pocket
portion according to the present invention has a smaller diameter
than that of the first pocket portion, formed to be lower than the
susceptor, and comprises a vertical wall continuing to the shelf
portion of the first pocket portion and a horizontal surface (the
horizontal surface itself does not have to be continuously
horizontal) continuing to the vertical wall. Also, the second
pocket portion according to the present invention is an N-th pocket
portion other than the first pocket portion, that is, concepts of a
third pocket portion and forth pocket portion . . . are included in
addition to the second pocket portion coming physically second.
Namely, a plurality of pocket portions having a smaller diameter
than that of the first pocket portion and formed to be lower than
the susceptor are all included.
[0017] Also, the susceptor according to the present invention is
configured to include at least a first structure having a first
pocket portion for loading an outer circumferential portion of a
wafer and a second structure provided below the first structure via
a fluid passage configured by a clearance between itself and the
first structure, the fluid passage may be configured to have one
end opening on the second vertical wall surface on a lower side of
the first pocket portion and the other end opening on the back
surface or side surface of the susceptor.
[0018] Namely, the fluid passage according to the present invention
is not limited to the embodiment of providing holes on the
susceptor structure, and the susceptor itself may be configured by
combining a plurality of structures, forming a clearance by
surfaces of two structures put together and using the same as a
fluid passage. When applying such configuration as above to prevent
irradiation of radiant heat from the heat source directly to the
wafer back surface, one end of the clearance as a fluid passage
formed between the first structure and second structure opens on
the vertical wall positioned below the first pocket portion. As a
result, the vertical wall becomes substantially perpendicular to
the wafer back surface, so that irradiation of radiant heat from
the heat source directly to the wafer back surface is prevented.
Note that the other end of the fluid passage may open on the back
surface of the susceptor or on the side surface of the
susceptor.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is a schematic sectional view showing an embodiment
of a vapor-phase growth reactor, wherein a susceptor according to
the present invention is applied.
[0020] FIG. 2 is a half plan view and half sectional view showing
an embodiment of a susceptor according to the present
invention.
[0021] FIG. 3 is a half sectional view showing another embodiment
of a susceptor according to the present invention.
[0022] FIG. 4 is a half plan view and half sectional view showing
still another embodiment of a susceptor according to the present
invention.
[0023] FIG. 5 is a half sectional view showing still another
embodiment of a susceptor according to the present invention.
[0024] FIG. 6 is a graph showing a resistivity distribution of
examples and comparative examples of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0025] Below, embodiments of the present invention will be
explained based on the drawings.
[0026] FIG. 1 is a schematic sectional view showing a single wafer
vapor-phase growth reactor 1, wherein an epitaxial film forming
chamber 2 formed by attaching an upper dome 3 and a lower dome 4 to
a dome mount 5 is provided. The upper dome 3 and the lower dome 4
are formed by a transparent material, such as quartz, and halogen
lamps 6a and 6b as heat sources are arranged above and below the
device 1 to heat a susceptor 10 and a wafer W.
[0027] The susceptor 10 is supported at its outer circumferential
portion of a lower surface thereof by fitting with a support arm 8
connected to a rotation axis 7 and rotated by driving the rotation
axis 7. A material of the susceptor 10 is not particularly limited
and, for example, a carbon base material coated with a SiC film
thereon is preferably used. A shape thereof will be explained later
on. Note that a method of conveying the wafer W into the susceptor
10 and conveying the wafer W out from the susceptor 10 is not
particularly limited, and either of a type of reloading the wafer
by moving a conveyor jig up and down by using a Bernoulli chuck and
a type of supporting a wafer lower surface by pins and reloading by
moving the pins up and down may be applied.
[0028] A side surface of the dome mount 5 is provided with a first
gas inlet 11 and a second gas inlet 12, and a side surface facing
thereto of the dome mount 5 is provided with a first gas outlet 13
and a second gas outlet 14. A reaction gas, such as SiHCl.sub.3,
obtained by diluting a Si source by a hydrogen gas and mixing the
result with a minute quantity of dopant is supplied from the first
gas inlet 11 to the forming chamber 2, and the supplied reaction
gas passes through a surface of the wafer W to grow an epitaxial
film and, then, discharged from the first gas outlet 13 to the
outside of the device 1.
[0029] Note that a carrier gas, such as a hydrogen gas, is supplied
from the second gas inlet 12 toward the lower surface side of the
susceptor 10 and discharged from the second gas outlet 14 provided
on the downstream side of the carrier gas to the outside of the
device 1. As a result, dopant released from the back surface of the
wafer can be discharged to the outside of the device 1 more
efficiently. Note that in the present invention, supply of a
carrier gas, such as a hydrogen gas, from the second gas inlet 12
into the forming chamber 2 is not essential, so that the second gas
inlet 12 and the second gas outlet 14 may be omitted if necessary.
Also, when providing the second gas inlet 12 to supply a hydrogen
gas or other carrier gas into the forming chamber 2, the first gas
outlet 13 for discharging a reaction gas, etc. for epitaxial growth
may be also used as the second gas outlet 14 without providing the
second gas outlet 14.
[0030] Next, the configuration of the susceptor 10 according to the
present embodiment will be explained.
[0031] As shown in FIG. 2(A)(B), on an upper surface of the
susceptor 10 in this example, a wafer pocket 101 made by a recessed
portion having a little larger diameter than an outer diameter of
the wafer W is formed. The wafer pocket 101 is composed of a first
pocket portion 102 for supporting the wafer W by point contact,
line contact or plane contact only with an outer circumferential
portion W1 of the wafer W and a second pocket portion 103 having a
smaller diameter than that of the first pocket portion 102 and
formed on the lower side of the susceptor 10; and the wafer W is
loaded so as to form a space between the back surface of the wafer
and the bottom surface 103b of the second pocket portion 103 at the
center of the first pocket portion 102. Note that the first pocket
portion 102 is configured by a first vertical wall 102a
corresponding to a vertical wall of the recessed portion and a
shelf portion 102b for supporting by contacting with the outer
circumferential portion W1 of the wafer W, and the second pocket
portion 103 is configured by a second vertical wall 103a
corresponding to a vertical wall of the recessed portion and a
bottom surface 103b corresponding to a horizontal surface of the
recessed portion.
[0032] As a result, flowing of a carrier gas to the back surface
side of the wafer is promoted and an effect of discharging dopant
released from the back surface of the wafer is enhanced. Note that
the shelf portion 102b of the first pocket portion may be formed to
be a tapered shape having a slope dropping from the outer
circumferential side to the inner circumferential side as
illustrated so as to support the outer circumferential portion W1
of the wafer W by line contact. Alternately, concave and convex
portions may be provided on a surface of the shelf portion 102b to
support the outer circumferential portion W1 of the wafer W by
point contact.
[0033] Particularly, as shown in the sectional view in FIG. 2(B),
the susceptor 10 of the present embodiment is provided with a fluid
passage 105, wherein one end 105a opens on a second vertical wall
103a of the second pocket portion and the other end 105b opens on
the back surface 104 of the susceptor 10. The fluid passage 105 is
composed of a plurality of holes formed in the circumferential
direction of the susceptor 10 as shown in the plan view in FIG.
2(A). The fluid passage 105 in this example is for discharging
dopant diffused from the wafer back surface W2 by heating at the
time of vapor-phase growing or dopant released from the wafer back
surface W2 by vapor-phase etching from the lower surface of the
susceptor 10 to prevent flowing of the dopant to the wafer front
surface W3 side.
[0034] Additionally, the fluid passage 105 in this example has a
shape, by which radiant heat H from the halogen lamp 6b provided
below the device 1 does not directly irradiate the wafer back
surface W2 via the fluid passage 105. As a result, radiant heat H
emitted from the halogen lamp 6b is prevented from directly
irradiating the wafer back surface W2 through the fluid passage
105, so that it is possible to prevent arising of a temperature
difference between a temperature of a part facing to the part
provided with the fluid passage 105 on the wafer W and a
temperature of a part facing to a not provided part, consequently,
generation of growth unevenness on the epitaxial layer and the
wafer back surface can be prevented.
[0035] A shape of the fluid passage 105 according to the present
invention is not specifically limited as far as it is shaped, so
that radiant heat H from the halogen lamp 6b provided below the
device 1 does not directly irradiate the wafer back surface W2 via
the fluid passage 105. Typical modification examples are shown in
FIG. 3(A) to (H). The fluid passage 105 shown in FIG. 3(A) is
configured to have one end 105a opening on the second vertical wall
103a of the second pocket portion and the other end 105b opening on
the side surface 106 of the susceptor 10. According to the fluid
passage 105 of this example, it is possible to prevent radiant beat
from the halogen lamp 6b from directly irradiating the wafer back
surface W2 more comparing with the example shown in FIG. 2.
[0036] Also, the fluid passage 105 shown in FIG. 3(B) is the same
as the example shown in FIG. 2 in a point that it is configured to
have one end 105a opening on the second vertical wall 103a of the
second pocket portion and the other end 105b opening from the
second vertical wall 103a of the second pocket portion to the
outside, which is the back surface 104 of the susceptor 10;
however, a shape of the fluid passage 105 is not a linear shape and
is formed to be a curved nonlinear shape. Accordingly, radiant heat
from the halogen lamp 6b enters to the middle of the fluid passage
105 but the radiant heat is blocked at a curved portion of the
fluid passage 105 and does not go further to the wafer back surface
W2 direction.
[0037] The fluid passage 105 shown in FIG. 3(C) is the same as the
example shown in FIG. 3(B) in points that it is configured to have
one end 105a opening on the second vertical wall 103a of the second
pocket portion and the other end 105b opening to the outside from
the second vertical wall 103a of the second pocket portion, which
is a back surface 104 of the susceptor 104, and also a curved
portion is provided in the middle of the fluid passage 105;
however, an inner diameter of the fluid passage 105 on the other
end 105b side is formed to be larger than an inner diameter of the
fluid passage 105 on the end 105a side.
[0038] The fluid passage 105 of the example shown in FIG. 3(D) is
the same as the examples shown in FIGS. 3(B) and (C) in a point
that it has one end 105a opening on the second vertical wall 103a
of the second pocket portion and the other end 105b opening to the
outside from the second vertical wall 103a of the second pocket
portion, which is a back surface 104 of the susceptor 104; but is
different in a point that the fluid passage 105 is formed to be a
linear shape.
[0039] The example shown in FIG. 3(E) is formed that the fluid
passages 105 are arranged one above the other, so that openings of
one ends 105a are arranged one above the other on the second
vertical wall 103a.
[0040] The fluid passage 105 of an example shown in FIG. 3(F) is
the same as the examples shown in FIGS. 3(B) and (C) in a point
that it has one end 105a opening on the second vertical wall 103a
of the second pocket portion and the other end 105b opening to the
outside from the second vertical wall 103a of the second pocket
portion, which is a back surface 104 of the susceptor 104 and is
the same as the example shown in FIG. (3D) in a point that the
fluid passage 105 is formed to be a linear shape; however, it is
different in a point that a recessed portion 103c is formed on an
outer circumference of the bottom surface 103b of the second pocket
portion 103 and a point that the bottom surface 103b of the second
pocket portion 103 is formed to be shallower comparing with that in
the examples in FIG. 3(A) to (B). Also, one end 105a of the fluid
passage 105 opens on the second vertical wall 103a corresponding to
the recessed portion 103c. Note that the recessed portion 103c of
the second pocket portion 103 may be formed continuously over the
outer circumference or discontinuously. The fluid passage 105 of
this example is also shaped, so that radiant heat H from the
halogen lamp 6b provided below the device 1 does not directly
irradiate the wafer back surface W2 via the fluid passage 105.
[0041] When the bottom surface 103b of the second pocket portion
103 is formed shallow as explained above, radiant heat from the
back surface of the susceptor 10 easily transfer to the inner
circumferential portion of the wafer W and a temperature difference
from a temperature of the outer circumferential portion of the
wafer becomes small. As a result, the slip dislocation of the wafer
deemed to be caused by thermal stress by the temperature difference
is prevented.
[0042] The fluid passage 105 of an example shown in FIG. 3(G) is
the same as the example shown in FIG. 3(F) in a point that the
recessed portion 103c is formed on an outer circumference of the
second pocket portion 103, but the recessed portion 103c is
configured only by a slope dropping toward the outer side. One end
105a of the fluid passage 105 opens on the second vertical wall
103a corresponding to the recessed portion 103c formed by the
slope. Note that the recessed portion 103c of the second pocket
portion 103 may be formed continuously over all outer circumference
or discontinuously. The fluid passage 105 of this example is also
shaped, so that radiant heat H from the halogen lamp 6b provided
below the device 1 does not directly irradiate the wafer back
surface W2 via the fluid passage 105.
[0043] The example shown in FIG. 3(H) is the same as the example
shown in FIG. 3(F) in a point that the recessed portion 103c is
formed on an outer circumference of the second pocket portion 103,
but is different in a point that a third vertical wall 103d is
furthermore provided in addition to the second vertical wall 103a
of the second pocket portion 103 and faces to the same. Also, the
bottom surface 103b of the second pocket portion 103 is formed to
be shallow in the same way as in the examples of FIGS. 3(F) and
(G). One end 105a of the fluid passage 105 opens on the third
vertical wall 103d of the recessed portion 103c, the other end 105b
opens to the inside from the second vertical wall 103a of the
second pocket portion, which is a back surface 104 of the susceptor
10, and the fluid passage 105 is formed to be a linear shape. Note
that the recessed portion 103c of the second pocket 103 may be
formed continuously over all outer circumference or
discontinuously. The fluid passage 105 of this example is also
shaped, so that radiant heat H from the halogen lamp 6b provided
below the device 1 does not directly irradiate the wafer back
surface W2 via the fluid passage 105.
[0044] The susceptor 10 according to the present invention may be
furthermore modified. FIG. 4 is a half plan view and half sectional
view showing still another embodiment of the susceptor according to
the present invention. In this example, the susceptor 10 itself is
configured by combining two structures 10a and 10b, and a clearance
is formed between the surfaces of putting the two structures 10a
and 10b together and used as a fluid passage 105.
[0045] Namely, as shown in FIG. 4(B), the susceptor 10 of this
example is configured by putting the first structure 10a on the
second structure 10b, and a fluid passage 105 is formed as a
clearance between the surfaces of putting the first and second
structures 10a and 10b together.
[0046] To put the first structure 10a on the second structure 10b
by leaving a clearance, an outer circumferential portion of an
upper surface of the second structure 10b has three protrusions 107
formed at positions at regular intervals of, for example, 120
degrees as shown by a dotted line in FIG. 4(A). Also, on an outer
circumferential portion on a back surface of the first structure
10a, groove portions 108 for receiving the protrusions 107 are
formed at proper positions corresponding to the protrusions 107
(meaning proper positions for a positional relationship of the
first structure 10a and the second structure 10b). If it is only
for supporting the first structure 10a by the second structure 10b,
the object is attained by providing protrusions 107 at least at
three positions without providing groove portions 108, however, by
providing the groove portions 108 at proper positions corresponding
to the protrusions 107 as in this example, a function of aligning
at the time of matching the first structure 10a with the second
structure 10b is also given. The protrusions 107 correspond to the
support means according to the present invention, and the
protrusions 10 and the groove portions 108 correspond to the
aligning means according to the present invention.
[0047] When configuring the susceptor 10 by putting the two
structures 10a and 10b together as explained above, the whole
circumference formed by the surfaces of the structures 10a and 10b
put together becomes a fluid passage 105, so that dopant released
from the wafer back surface W2 at the time of vapor-phase growth
can be furthermore effectively discharged from the fluid passage
105 formed by the whole circumference without letting it flow to
the wafer front surface W3. Also, the fluid passage 105 is formed
by a clearance by simply putting the first structure 10a and the
second structure 10b together without forming a hole to be a fluid
passage 105, it is convenient in terms of processing.
[0048] A shape of the susceptor 10 shown in FIG. 4 is not
specifically limited as far as it forms a clearance to configure
the fluid passage 105 on the surfaces put together at the time of
putting the first structure 10a and the second structure 10b
together and, furthermore, the fluid passage 105 as the clearance
becomes a shape for preventing radiant heat from the halogen lamp
6b provided below the device 1 from directly irradiating the wafer
back surface W2 via the fluid passage 105. Typical modification
examples are shown in FIG. 5(A) to (C).
[0049] The susceptor 10 shown in FIG. 5(A) is configured that the
fluid passage 105 formed by the surfaces of the first structure 10a
and the second structure 10b put together becomes a curved shape as
shown in FIG. 3(B), wherein protrusions 107 are provided at three
positions at regular intervals on the back surface of the first
structure 10a, and the first structure 10a is supported by the
second structure 10b as a result that the protrusions 107 contact
with edges on the surface of the second structure 10b.
[0050] Also, the susceptor 10 shown in FIG. 5(B) is also configured
that a shape of the fluid passage 105 becomes a curved shape in the
same way as the fluid passage 105 shown in FIG. 5(A), wherein in
addition to forming the protrusions 107 as a support means on the
surface of the second structure 10b, protrusions 109 as an aligning
means are formed on a side surface of the second structure 10b and
a proper position of the first structure 10a and the second
structure 10b is determined as a result that the protrusions 109
contact with the side wall on the back surface of the first
structure 10a.
[0051] Furthermore, the susceptor 10 shown in FIG. 5(C) is also
configured that a shape of the fluid passage 105 becomes a curved
shape in the same way as the fluid passage 105 shown in FIG. 5(A)
and the protrusions 107 as a support means are formed on the
surface of the second structure 10b; wherein protrusions 109 as an
aligning means are formed on the side wall on the back surface of
the first structure 10a and a proper position of the first
structure 10a and the second structure 10b is determined as a
result that the protrusions 109 contact with the side surface of
the second structure 10b.
[0052] In any of the susceptors 10 shown in FIG. 5(A) to (C), the
whole circumference formed by the surfaces of the structures 10a
and 10b put together becomes the fluid passage 105 in the same way
as the susceptor 10 shown in FIG. 4, so that dopant released from
the wafer back surface W2 at the time of vapor-phase growth can be
furthermore effectively discharged from the fluid passage 105
formed by the whole circumference without letting it flow to the
wafer front surface W3. Also, the fluid passage 105 is formed by a
clearance by simply putting the first structure 10a and the second
structure 10b together without forming a hole to be a fluid passage
105, it is convenient in terms of processing.
[0053] Furthermore, the fluid passage 105 has a shape that radiant
heat emitted from the halogen lamp 6b does not directly irradiate
the wafer back surface W2 through the fluid passage 105, so that it
is possible to prevent arising of a temperature difference between
a temperature of a part facing to the part provided with the fluid
passage 105 on the wafer W and a temperature of a part facing to a
not provided part, consequently, generation of growth unevenness on
the epitaxial layer and the wafer back surface can be
prevented.
[0054] Note that the embodiments explained above are described to
facilitate understanding of the present invention and is not to
limit the present invention. Accordingly, respective elements
disclosed in the above embodiments include all design modifications
and equivalents belonging to the technical scope of the present
invention.
[0055] For example, the susceptor of the present invention was
explained by taking the single wafer vapor-phase growth reactor 1
as an example in the above embodiment, however, the susceptor of
the present invention is not limited to that and may be naturally
applied to a conventionally used batch vapor-phase growth reactor
for performing processing on a plurality of wafers at a time.
EXAMPLES
[0056] Below, examples of the present invention will be explained
by comparing with comparative examples to clarify the effects of
the present invention.
[0057] As a unified condition of examples and comparative examples,
a P.sup.+ type silicon monocrystal wafer having a diameter of 200
mm, a main surface in a surface direction of (100) and resistivity
of 15 m .OMEGA.cm was used to grow on the wafer surface a P type
epitaxial film having a thickness of about 6 .mu.m and resistivity
of 10 .OMEGA.cm at an epitaxial growth temperature of 1125.degree.
C. by performing hydrogen baking at 1150.degree. C. for 20 seconds
and supplying a mixed reaction gas obtained by diluting SiHCl.sub.3
as a silicon source and B.sub.2H.sub.6 as a boron-dopant source by
a hydrogen gas into the vapor-phase growth reactor.
[0058] In the examples, the single wafer vapor-phase growth reactor
shown in FIG. 1 was used and a susceptor having a shape shown in
FIG. 3(C) was used. Specifically, holes composing a fluid passage
(a large hole width was 2 mm, a small hole diameter was 1 mm .phi.,
and a slit shape having a width of 2 mm) were formed allover the
second vertical wall at 4 mm pitch intervals (a distance between
centers of the slits).
[0059] In comparative examples, in the same way as in the examples,
the single wafer vapor-phase growth reactor shown in FIG. 1 was
used, but a fluid passage was not formed in the susceptor.
[0060] In respective epitaxial silicon wafers obtained as the
examples and comparative examples, a dopant concentration
distribution in the radial direction in the epitaxial film was
measured on a region from an outer circumferential end to 100 mm by
using an SCP device (Surface Charge Profiler). Based on the
measurement results, a resistivity distribution in the radial
direction in the epitaxial film was obtained. The results are shown
in FIG. 6.
[0061] As is obvious from FIG. 6, it was confirmed that a P type
epitaxial film having a resistivity of 10 .OMEGA.cm was obtained
uniformly on the surface as desired. On the other hand, in the
comparative examples, a resistivity distribution was confirmed to
be widely declined on the outer circumferential portion.
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